1. Technical Field of the Invention
The present invention relates to a packaged semiconductor, a semiconductor package and a method for fabricating the package, and more particularly but not by way of limitation, to a thin semiconductor package having improvements in heat radiation and a method for manufacturing the same.
2. History of Related Art
It is conventional in the electronic industry to encapsulate one or more semiconductor devices, such as integrated circuit dies, or chips, in a semiconductor package. These plastic packages protect a chip from environmental hazards, and provide a method of and apparatus for electrically and mechanically attaching the chip to an intended device. Recently, such semiconductor packages have included metal lead frames for supporting an integrated circuit chip which is bonded to a chip paddle region formed centrally therein. Bond wires which electrically connect pads on the integrated circuit chip to individual leads of the lead frame are then incorporated. A hard plastic encapsulating material, or encapsulant, which covers the bond wire, the integrated circuit chip and other components, forms the exterior of the package. A primary focus in this design is to provide the chip with adequate protection from the external environment in a reliable and effective manner.
As set forth above, the semiconductor package therein described incorporates a lead frame as the central supporting structure of such a package. A portion of the lead frame completely surrounded by the plastic encapsulant is internal to the package. Portions of the lead frame extend internally from the package and are then used to connect the package externally. More information relative to lead frame technology may be found in Chapter 8 of the book Micro Electronics Packaging Handbook, (1989), edited by R. Tummala and E. Rymaszewski and incorporated by reference herein. This book is published by Van Nostrand Reinhold, 115 Fifth Avenue, New York, N.Y.
Once the integrated circuit chips have been produced and encapsulated in semiconductor packages described above, they may be used in a wide variety of electronic appliances. The variety of electronic devices utilizing semiconductor packages has grown dramatically in recent years. These devices include cellular phones, portable computers, etc. Each of these devices typically include a motherboard on which a significant number of such semiconductor packages are secured to provide multiple electronic functions. These electronic appliances are typically manufactured in reduced sizes and at reduced costs, consumer demand increases. Accordingly, not only are semiconductor chips highly integrated, but also semiconductor packages are highly miniaturized with an increased level of package mounting density.
According to such miniaturization tendencies, semiconductor packages, which transmit electrical signals from semiconductor chips to motherboards and support the semiconductor chips on the motherboards, have been designed to have a small size. By way of example only, such semiconductor packages may have a size on the order of 1xc3x971 mm to 10xc3x9710 mm. Examples of such semiconductor packages are referred to as MLF (micro leadframe) type semiconductor packages and MLP (micro leadframe package) type semiconductor packages. Both MLF type semiconductor packages and MLP type semiconductor packages are generally manufactured in the same manner.
Such conventional semiconductor packages are not without problems. Specifically, a typical semiconductor package is difficult to make slim because the thickness of the internal leads is equivalent to the thickness of the chip paddle. Further, the mounting of the semiconductor chip on the chip paddle increases the overall thickness of the package. The thickness is increased because of the input/output pads on the semiconductor chip mounted on the chip paddle are positioned at a higher level than the internal leads, thereby increasing the loop height of the conductive wires. The increased height may contribute to wire sweeping, caused by the encapsulation material during encapsulation.
In addition, mounting the semiconductor chip on a chip paddle having an externally exposed bottom surface has poorer heat radiation than having a direct externally exposed bottom surface of the semiconductor chip.
Finally, after the chip-mounting step and wire-bonding step are performed, the semiconductor package is encapsulated only after the leadframe is positioned on a mold. Thus, although the leadframe is in close contact with the lower mold die, some encapsulation material infiltrates through the interface between the leadframe and the lower mold die, resulting in the formation of so-called xe2x80x9cflashxe2x80x9d. An extra de-flashing step must then generally be executed.
In one embodiment of the present invention, there is provided a semiconductor package comprising a semiconductor chip having an upper surface and a bottom surface. A plurality of input bond pads and output bond pads on the upper surface of the semiconductor chip and along the circumference of the semiconductor chip are electrically connected to the semiconductor chip. A chip paddle may be provided which has a top surface, a side surface and a bottom surface. The chip paddle is bonded to the bottom surface of the semiconductor chip by an adhesive. The chip paddle has corners, a circumference and a half-etched section at the lower edge of the chip paddle along the chip paddle circumference.
A lead frame is provided having a plurality of tie bars. Each of the tie bars has a side surface and a bottom surface. The plurality of tie bars are connected to the corners of the chip paddle. The plurality of the tie bars externally extend from the chip paddle and have a half-etched section. A plurality of dam bars are provided on the lead frame help limit flow of encapsulation material on the leadframe.
A plurality of internal leads connect to the leadframe. Each of the leads has a side surface and a bottom surface. The leads are radially formed at regular intervals along and spaced apart from the circumference to the chip paddle and extend towards the chip paddle. Each of the leads has a step shaped half-etched section facing the chip paddle.
A plurality of via conductive wires are electrically connected to and between the plurality of leads and the semiconductor chip. Encapsulating material encapsulates the semiconductor chip, conductive wires, chip paddle, and the leads to form a package body. The flow of the encapsulation material is limited by the dam bars formed on the leadframe. The dam bars also serve to stabilize the leads on the leadframe. After encapsulation, the chip paddle, leads, and tie bars are externally exposed at respective side and bottom surfaces.
A ground ring may be provided on the leadframe having an upper surface and a lower surface. The conductive wires may be connected to the ground ring, which is exposed at the lower surface. The ground ring may further serve to function as a power ring.